Alternating current static control system

ABSTRACT

An alternating current solid state control system utilizing alternating current AND and OR alternating current solid state control logic elements. The alternating current logic elements perform their logic functions by comparing the voltage drop across a resistor to a predetermined reference voltage, the voltage drop being caused by the logical input state of the logic element. Each element&#39;&#39;s output can be used as a feedback to its own inputs or can be connected to the inputs of electrically similar circuits. By the use of multiple logical inputs, various feedback connections, and various combinations of the alternating current logic elements complex logic functions can be generated to control mechanical apparatus.

United States Patent Kosco [451 Aug. 15, 1972 [72] Inventor: William C.Kosco, Southfield, Mich.

[73] Assignee: La Salle Machine Tool, Inc., Warren, Mich.

221 Filed: July 26, 1971 21 Appl.No.: 166,056

[52] US. Cl. ..3l7/l48.5 R, 307/210 [51] Int. Cl. ..l-l0lh 47/32 [58]Field of Search ..307/210; 317/134, 148.5 R, 317/1485 B [56] ReferencesCited UNITED STATES PATENTS 2,748,269 5/1956 Slutz ..307/210 X 3,026,5053/1962 Bevilacqua ..3 17/ 148.5 B

3,329,869 7/1967 Obenhaus ..317/148.5 B

Primary Examiner-A. D. Pellinen Attorney-Finn G. Olsen et a1.

[5 7] ABSTRACT An alternating current solid state control systemutilizing alternating current AND and OR alternating current solid statecontrol logic elements. The alternating current logic elements performtheir logic functions by comparing the voltage drop across a resistor toa predetermined reference voltage, the voltage drop being caused by thelogical input state of the logic element. Each elements output can beused as a feedback to its own inputs or can be connected to the inputsof electrically similar circuits. By the use of multiple logical inputs,various feedback connections, and various combinations of thealternating current logic elements complex logic functions can begenerated to control mechanical apparatus.

10 Claims, 2 Drawing Figures PATENTEDAus 15 I972 F om INVENTOR WILLIAMC. KOSCO ATTORNEYS ALTERNATING CURRENT STATIC CONTROL SYSTEM BACKGROUNDOF THE INVENTION The use of electronic elements for generating logicfunctions for mechanical apparatus control such as machine control iswell known. Such logic control has conventionally been accomplished bythe use of direct current logic elements. While machine tools andassociated apparatus such as motors, starters, solenoids, etc., usedalternating current, the logic control elements required direct current.Therefore an expensive and complex AC to DC conversion was necessary.This invention will eliminate the problems of AC to DC conversionconventionally required in machine tool control systems. Complex logicfunctions can be generated directly from AC signals by usingcombinations of AC logic elements, feedback loops, and multiple functioninputs. The complex functions can then be amplified and used directly tocontrol AC mechanical apparatus.

SUMMARY OF THE INVENTION The system of this invention employs a solidstate parallel logic network in which all input and output signaldevices are connected to a common power bus. This enables the AC logiccomponents to display their signal status totally independent of anyother signal condition. The logical state of an element can thus bedetermined without knowledge of the logical state of an adjacentelement, unlike conventional systems which use serial logic or relaydevices. The system of this invention is assembled so that apredetermined voltage drop across a resistor in the system occurs inresponse to the existence of the logic function which the system is toperform. In response to the existence of this voltage drop, current froma reference voltage line can flow through the resistor so as to triggeran associated transistor and provide for the desired current flowindicating the existence of the predetermined logic function. Morespecifically, in the AND gate form of applicants system, thepredetermined voltage drop across the resistor occurs only whenconditions exist allowing current to flow through all of the input linesin the AND gate system. In the OR gate system of this invention, thepredetermined voltage drop across the resistor occurs in response toflow of current through any one of the input lines for the OR gatesystem. As a result, the system of this invention enables the performingof logic functions corresponding to the logic functions obtainable withconventional DC solid state control logic elements directly from the ACsignals thus eliminating the conventional requirement for initiallyconverting AC to DC signals.

Each element can be designed with a number of inputs configured intovarious logical functions. While as a practical matter there is a limiton the number of inputs, the ability to use the low power output of alow output power logic element as a feedback to its own inputs or todrive the inputs of other electrically similar elements yields thepossibility of generating an infinite number of logic functions to beused in controlling mechanical apparatus. After the desired function hasbeen generated for the specific application a high output power AC logicelement provides a high power output to the actual mechanical apparatusto be controlled.

Further objects, features and advantages of this invention will becomeapparent from a consideration of the following description, the appendedclaims, and the accompanying drawing in which:

FIG. 1 is the logical function diagram; and

FIG. 2 is the wiring schematic for implementation of the logicalfunction of FIG. 1.

With reference to FIG. 1, the block diagram shows a multiple input logicelement system 1, indicated by the broken line, with its low poweroutput 2 being used as a feedback to input line 4 and being used todrive an electrically similar input line 5 of logic element system 6.The high power output 8 of logic element 6 is connected to an AC load 13(e.g. solenoid, starter, etc.

Various combinations of input signals will give an output at 8. If thepresence of a signal is a l state and the absence of a signal is an 0"state then a 1" on lines 14 and 16 will produce a l on line 18, a l online 20, a l on line 2, a l at the feedback input line 4, and a l atinput line 5 of logic element 6. If then line 14 subsequently returns toa 0 the l at line 4 will maintain the output 2 of system 1 in a 1"state. The addition of a 1" at line 22 will then produce a l at output 8which drives the AC load 13.

With reference to FIG. 2, the switches 24, 26 and 32 are connected tothe respective input lines l4, l6, and 22. Closing a switch produces asignal condition or a I state. An open switch represents no signal or an0 state. Thus as the description will demonstrate, the circuit canperform the same complex logic functions of the block diagram of FIG. 2using AC signals to perform those logical functions.

The lines L, and L, are connected to a conventional AC voltage sourcewith a voltage thereacross of for example llO volts. LR, and LR arereference voltages obtained through an intermediate connection toautotransformers 33 and 35 respectively, the voltage from L, to LR, orLR being for example 40 volts. The purpose of system 1 is to providecurrent through transistor 34 in response to a predetermined voltagecondition on either resistor 36, 38, or 40.

The predetermined voltage drop on resistor 36, for example, that causescurrent to flow in circuit 42 through base current limiting resistor 44is established by biasing resistor 46 connected to base 48 and emitter50 of transistor 34. In the circuit 1, limit switch 26 and manual switch24 connect L, to the input lines 16 and 14, respectively. When bothswitches 26 and 24 are closed, for example, and during the AC half cyclewhen L, is negative with respect to L current flowing from L to L, isdiverted from a path through resistor 52, diode 54, resistor 36, anddiode 55 to a path comprising resistor 52, diode 56, and limit switch26, and from a path through resistor 58, diode 60, resistor 36, anddiode 55 to a path comprising resistor 58, diode 62, and manual switch24 due to the lower impedance of the path through diode 56 and 62. Withless resultant current flow through resistor 36 the voltage dropdecreases and current flows through circuit 42, diode 64, and resistor36. The same result can be accomplished by causing a signal like L to beimposed on input 4 such as the feedback input even if switch 24 issubsequently opened. In a like manner resistors 38 or 40 can beconditioned to provide current flow in circuit 42.

When the predetermined voltage condition exists and transistor 34conducts, current flows in current limiting resistor 66 tosimultaneously charge capacitor 68 and provide current to the base 70 oftransistor 72 through the base current limiting resistor 74. Because ofbiasing resistor 76, transistor 72 conducts thereby connecting output 2to L, through level shifting diodes 78, 79, 80, AC isolation diode 55,and reverse voltage breakdown protection diode 84. During the next AChalf cycle when L, is positive with respect to L transistors 34 and 72cease conducting, capacitor 68 slowly discharges through resistors 74and 76 and various transistor leakage paths, and output 2 is connectedto L, through resistor 86. During the next half cycle when L, is againnegative with respect to L the capacitor 68 performing a short durationmemory function provides base drive current to transistor 72 toinitially drive it into conduction. This in turn provides a feedbacksignal to input line 4 initially so that the input function of a l atline 4 and 16 is satisfied even if line 14 has gone back to a state. Ifswitch 26 remains closed, transistor 34 will conduct again, charging thecapacitor 68 and so forth until such time as line 16 returns to O, andthe voltage drop on resistor 36 no longer provides for current fiow incircuit 42. The signal generated at output 2 representing a signalcondition is in reality not a full wave sine wave identical to L, but isa half wave rectified sine wave with negative peaks corresponding to thenegative peaks of L,. This low power signal would generally be incapableof driving an AC machine device, but it can be used just as L, can beused as a logic signal to drive input 4 and 5, for example.

If output 2 remains in he output condition representing a I stateprovided by switch 26 closed and the feedback combination just describedrepresenting a l state, and switch 32 is closed, current flowing from Lto L, is diverted from a path comprising resistor 88, diode 90, andresistor 92 to a lower impedance path comprising diode 94, input line 5,output line 2, diode 84, transistor 72, diodes 78-80, and diode 55 andfrom a path comprising resistor 96, diode 98, and resistor 92 to a lowerimpedance path comprising resistor 96, diode 100, and manual switch 32.With less resultant current in resistor 92 the voltage drop thereacrossdecreases and current will flow from LR, to L, through the base circuit101 of transistor 102 comprising the parallel combination of coil 104and capacitor 106, biasing resistor 108, base current limiting resistor110, and reverse voltage protection diode 112. This base current causestransistor 102 to conduct and current flows in limiting resistor 113toward L, thereby energizing relay coil 104 which activates relaycontacts 114 and simultaneously charging capacitor 106. The contacts 114in turn activate a conventional solid state Triac circuit 116 which canproduce a high powered output on line 8 capable of driving a solenoidload 13 for example.

During the second AC half cycle when L is negative with respect to L, nocurrent flows in circuit 101 or in transistor 102 due to theincompatibility of junction polarities. During this time period thecapacitor 106 serving as ashort duration memory discharges through coil104 thereby maintaining the coil 104 in the energized state until thenext AC half cycle when L, is negative with respect to L and thetransistor 102 can conduct again.

The output 8 of the Triac circuit 116 is a full wave high power outputcapable of driving an AC load as well as being used as a logic signal iffurther signal processing were desired.

Thus it becomes obvious that the system disclosed can provide anunlimited number of logical operations incorporating high and low powersignals, multiple inputs, multiple elements, and feedback control.

What is claimed is:

1. An alternating current logic control system comprising, a pair ofconductors connected to an alternating current source, a plurality ofinput lines connected to first resistor means so that in response to apredetermined logic function presented at said input lines apredetermined voltage drop condition will be created across said firstresistor means, third conductor circuit means connected to the saidfirst resistor means in which electric current flows in response to thesaid predetermined voltage drop, capacitor means in said third conductorcircuit means and in parallel with amplifier means each beingrespectively charged and energized when electric current flows in saidthird conductor circuit means, a feedback connection from the output ofsaid amplifier means to any of a plurality of said input lines, and anoutput connection from the output of said amplifier to input lines ofany similar logic control system so that various alternating currentlogic functions may be generated 2. An alternating current logic controlsystem of claim 1 wherein third conductor circuit means includes firsttransistor means connected to said first resistor means which conductswhen the predetermined voltage drop occurs at said first resistor means,second resistor means in the said third conductor circuit means toestablish said predetermined voltage level for conduction, thirdresistor means in said third conductor circuit means to provide electriccurrent limiting when said first transistor conducts, diode means insaid third conductor circuit means to provide reverse voltage breakdownprotection and alternating current isolation for said first transistormeans, and said first transistor means connected to said capacitor meansto charge the same during conduction of said first transistor means.

3. An alternating current logic control system of claim 2, wherein saidcapacitor means charged during conduction of said first transistor meansis a short duration memory means connected to the input of saidamplifier means to provide current to the same during the initial timeperiod when current polarity of said pair of conductors is again properfor said first transistor means to resume conduction, thus the feedbackconnection is maintained in the logic state previously generated whensaid first transistor means was conducting in response to a properlogical function on said input lines.

4. In an alternating current control system of claim 3, wherein saidinput lines include input diode means in each of said input lines todivert electric current in response to alternating current input signalsfrom said first resistor means so that said predetermined voltage dropin said first resistor means can be accomplished, fourth resistor meansconnected to said input diode means to provide a normal predeterminedcurrent level v providing a positive feedback circuit.

7. An alternating current logic control system of claim 5, wherein saidoutput connection includes a fifth conductor connecting the output ofsaid amplifier to any of a plurality of input lines of any other logiccontrol element being electrically similar but logically diverse.

8. An alternating current logic control system of claim 4 wherein saidamplifier means comprises inductively actuated relay means alternatinglyactuated by conduction of said first transistor means and discharge ofsaid capacitor means.

9. An alternating current logic control system of claim 8 wherein saidfeedback connection includes a fourth conductor connecting the output ofsaid amplifier means to any of a plurality of said input lines therebyproviding a positive feedback circuit.

10. An alternating current logic control system of claim 8, wherein saidoutput connection includes a fifth conductor connecting the output ofsaid amplifier means to an alternating current load.

l II l l

1. An alternating current logic control system comprising, a pair ofconductors connected to an alternating current source, a plurality ofinput lines connected to first resistor means so that in response to apredetermined logic function presented at said input lines apredetermined voltage drop condition will be created across said firstresistor means, third conductor circuit means connected to the saidfirst resistor means in which electric current flows in response to thesaid predetermined voltage drop, capacitor means in said third conductorcircuit means and in parallel with amplifier means each beingrespectively charged and energized when electric current flows in saidthird conductor circuit means, a feedback connection from the output ofsaid amplifier means to any of a plurality of said input lines, and anoutput connection from the output of said amplifier to input lines ofany similar logic control system so that various alternating currentlogic functions may be generated.
 2. An alternating current logiccontrol system of claim 1 wherein third conductor circuit means includesfirst transistor means connected to said first resistor means whichconducts when the predetermined voltage drop occurs at said firstresistor means, second resistor means in the said third conductorcircuit means to establish said predetermined voltage level forconduction, third resistor means in said third conductor circuit meansto provide electric current limiting when said first transistorconducts, diode means in said third conductor circuit means to providereverse voltage breakdown protection and alternating current isolationfor said first transistor means, and said first transistor meansconnected to said capacitor means to charge the same during conductionof said first transistor means.
 3. An alternating current logic controlsystem of claim 2, wherein said capacitor means charged duringconduction of said first transistor means is a short duration memorymeans connected to the input of said amplifier means to provide currentto the same during the initial time period when current polarity of saidpair of conductors is again proper for said first transistor means toresume conduction, thus the feedback connection is maintained in thelogic state previously generated when said first transistor means wasconducting in response to a proper logical function on said input lines.4. In an alternating current control system of claim 3, wherein saidinput lines include input diode means in each of said input lines todivert electric current in response to alternating current input signalsfrom said first resistor means so that said predetermined voltage dropin said first resistor means can be accomplished, fourth resistor meansconnected to said input diode means to provide a normal predeterminedcurrent level in said first resistor means when electric current is notbeing diverted through said input diode means in response to saidalternating current input signals.
 5. An alternating current staticcontrol system of claim 4, wherein said amplifier means comprisingsecond transistor means alternatingly driven into conduction by saidfirst transistor means and said capacitor means.
 6. An alternatingcurrent control system of claim 5, wherein said feedback connectionincludes a fourth conductor connecting the output of said amplifiermeans to any of a plurality of said input lines thereby providing apositive feedback circuit.
 7. An alternating current logic controlsystem of claim 5, wherein said output connection includes a fifthconductor connecting the output of said amplifier to any of a pluralItyof input lines of any other logic control element being electricallysimilar but logically diverse.
 8. An alternating current logic controlsystem of claim 4 wherein said amplifier means comprises inductivelyactuated relay means alternatingly actuated by conduction of said firsttransistor means and discharge of said capacitor means.
 9. Analternating current logic control system of claim 8 wherein saidfeedback connection includes a fourth conductor connecting the output ofsaid amplifier means to any of a plurality of said input lines therebyproviding a positive feedback circuit.
 10. An alternating current logiccontrol system of claim 8, wherein said output connection includes afifth conductor connecting the output of said amplifier means to analternating current load.